Sydney Centre in Geomechanics and Mining Materials

We are at the forefront of research in geomechanics and granular physics, and aim to broaden our world-leading position in fields such as mining geomechanics and bulk material handling.

About the centre

The Sydney Centre in Gemechanics and Mining Materials (SciGEM) within the School of Civil Engineering was established in 2013 to capitalise on the outstanding pool of researchers with specialised skills and expertise in the field of geomechanics and geotechnical engineering.

SciGEM’s objective is to remain world leaders in the research fields of geomechanics, geotechnical engineering and granular mechanics. We are expanding into newer geo-environmental research issues such as soil contamination and bulk materials handling issues, including silo flow and conveying of particles, using our specialist laboratories such as Dynamix. We are focused on furthering our collaborations and relationships with industry and government in these sectors.

Our research projects

Our primary research goal is to identify the emerging properties of granular materials and establish the fundamental understanding of how grains flow, segregate, mix and crush, by merging complementary analytical, experimental and computational tools. Using our wide range of in-house computational models we carry out direct and precise simulations, with which we complement the experimental findings and cover the broader conditions tackled by industry and nature.

We use this body of observations to articulate simple and general mathematical formulae that accurately predict granular flows, accounting for the effect of grain size, shape and interaction modes. Our findings have advanced the resolution of important problems in geotechnical engineerings (prediction of landslide paths, novel and traditional foundations, etc.), geophysics (earthquake dynamics, heat balance beneath volcanoes), and mining and manufacturing (optimisation of material handling and mixing processes).

The biggest problem with understanding granular problems is that we can't see inside them to observe what is happening. The DynamiX facility allows us to use large scale X-ray radiography and tomography to probe the internal structure of deforming granular materials, such as coffee, sand and snow. We have innovative methods for measuring the internal velocity fields, grain size distribution and particle shape orientation as they evolve over time. These methods have led to the investigation of a large number of problems, applicable to many industries, including bulk solids handling, coffee production and fibre-reinforced concrete.

The shear strength of granular materials is ultimately determined at the interface scale between two grains. Key parameters include contact stiffness, friction coefficient and capillary interaction. While connecting the microscopic quantities with the engineering applications, fitting procedures at the grain scale were often made to achieve good agreements with macroscopic benchmark experiments.

Rather than using this end to justify the fitting processes, we are looking at extracting measurable material properties at the lower scale(s). In particular, we employ mechanical and chemical surface treatment for alternating the surface structure, microscopy (optical profilometer, atomic force microscopy) for characterising the surface topology, and nano-indentation for mechanical testing of the surface interaction. With the coexistence of multiple phases (solid, gas and liquid) in granular materials, we examine the dynamic interplay among them via computational (molecular dynamics, smoothed particle hydrodynamics, discrete element method, and lattice Boltzmann method) and experimental approaches developed in the lab.

We are also developing numerical tools for generating, analysing and simulating rough surfaces, and finally integrate these interfacial information into a hierarchical constitutive framework to pass essential parameters (and their evolution) to the engineering scale.

The discipline of soil mechanics has historically focused on the behaviour of clayey sediments which underlie many of the world’s major cities and have presented many challenges to geotechnical engineering. Considerable research to understand the behaviour of sands which form extensive deposits, particularly around the coasts of many parts of the world, has revealed that the idealised soils tested in research laboratories do not represent real soils for which particle orientation and arrangement (structure) is important. There are many man-made (mined) soils that are intermediate between clays and sands.

Our research aims to better characterise these materials through careful testing in the laboratory using a range of soil testing apparatus. We conduct model experiments to evaluate the constitutive models developed from the material characterisation and use these models to investigate some challenging problems, such as understanding liquefaction in ship cargoes of mined ore materials; the onset of slope failures on submarine slopes; and the behaviour of soils subject to dynamic loading.